Recent developments in the field of computer controlled automated hydraulic and pneumatic equipment has resulted in a requirement for smaller more efficient solenoid valves which exhibit high reliability characteristics.
The prior art related to solenoid valves for control of fluids and gases includes numerous examples of devices each of which is characterized by the following construction. Conventional solenoid valves include a coil housing within which a solenoid coil is arranged so that when current is applied, a plunger, or armature is moved thereby opening or sealing an orifice. In order to prevent the fluid or gas from entering the solenoid housing, conventional solenoid valves utilize a flexible diaphragm which seals the cavity in which the solenoid coil and the plunger are mounted. During operation, when the solenoid coil is energized, the plunger bears against the diaphragm which, in turn, bears against a poppet member which seals the orifice. This poppet member usually has a conical portion, the larger base of which is larger than the orifice which is to be sealed and a cylindrical portion which slides within the orifice. In use the conical surface of the poppet member bears against the edge of the orifice thereby sealing the orifice.
The construction of conventional solenoid valves is subject to numerous deficiencies included among which is a need for careful alignment of the component parts in order to ensure that the line of action of the plunger is aligned with the poppet member in order to effect an adequate seal. This requirement leads to a need for close manufacturing tolerances on the various component parts and careful assembly procedures resulting in a relatively high unit cost. Even with close tolerance manufacture of the various components and careful assembly procedures, misalignment of the poppet member can occur, thereby resulting in leakage of the fluid and relatively low overall reliability. Even slight misalignment of the poppet member and the orifice results in an elliptical line of contact between the conical surface of the poppet member and the circular edge of the orifice requiring substantial force on the poppet member in order to deform the poppet member and the orifice seat to create a seal. This requirement for high seating force results in a need for a relatively large amount of electrical power resulting in a relatively low overall efficiency of the valve.
In a conventional solenoid valve the fluid which is controlled by the valve acts on virtually the entire diaphragm. In order to actuate the valve the solenoid coil and the armature or plunger must provide sufficient force to overcome the force of the fluid. This leads to a relatively high rate of power consumption.
Another source of malfunction in conventional solenoid valves is related to the conventional two piece construction of the diaphragm and poppet assembly. Because of the motion of these two components, the possibility of wear and degradation of the interface between the diaphragm and the poppet member exists. This wear can lead to misalignment, and ultimately failure of the diaphragm or the poppet member with the consequent failure of the entire solenoid valve.